Stress Increases In Compressive Steel Under Constant Load Caused By Shrinkage

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Title: Stress Increases In Compressive Steel Under Constant Load Caused By Shrinkage

Author(s): G. A. Maney and M. B. Lagaard

Publication: Journal Proceedings

Volume: 36

Issue: 6

Appears on pages(s): 541-552

Keywords: none

Date: 6/1/1940

Abstract:
Data from various sources, which have formed the basis of their conclusions that continued deforma- tions in compressive steel of reinforced concrete mem- bers under constant loads are caused by shrinkage and not by plastic flow or creep. This applies to the common case in practice where the compressive steel receives its load only through the bond in the concrete and not by direct application at the ends. They do not contend that flow of concrete does not occur under high loads, but present the opinion that a flow in bond occurs as well as a flow in com-pression, thereby causing no additional stress in the reinforcement. They explain the additional deforma- tion in a concrete column beyond that normally at- tributed to shrinkage, by an increase in load intensity due to reduction of the effective compression area from warping. This is caused by more rapid drying in the outside elements of the column. They present evidence to explain the high time-deformations on the compressive surface of plain concrete beams under sustained load, on the basis of eccentric shrink- age rather than flow. What is usually called flow or creep in a drying out column under sustained load is identified by them as shrinkage since changes of comparable magnitude are not found to occur in wet loaded columns. An attempt is made to reallocate the responsibility for time changes under load, between shrinkage and flow.